Bifocal multiorder diffractive lenses for vision correction

ABSTRACT

A bifocal multiorder diffractive lens is provided having a lens body with one or more first regions having a first multiorder diffractive structure providing near vision correction, and one or more second regions having a second multiorder diffractive structure providing distance vision correction, in which the lens defines an aperture divided between the first and second regions. Such one or more first regions may represent one or more annular rings, or other portion of the lens, and the second region may occupy the portion of the lens aperture outside the first region. The lens body may be provided by a single optical element or multiple optical elements. When multiple optical elements are used, the multiorder diffractive structures may be located along an interior surface of the lens. In other embodiments, a bifocal multiorder diffractive lens is provided by a single or multiple element lens body having a multiorder diffractive structure for distance vision correction and one or more refractive regions to add power for near vision correction, or a single or multiple element lens body shaped for refractive power for distance vision correction and a multiorder diffractive structure for add power for near vision correction. The lens may represent a contact lens, a spectacle lens, or the optic portion of an intraocular implant (IOL). Multiorder diffractive structures may be optimized for performance for photopic and scotopic vision.

FIELD OF THE INVENTION

The present invention related to multiorder diffractive lenses forvision correction, and particularly to bifocal multiorder diffractivelenses for therapeutic vision correction at distance and near visioncorrection suitable for use with a variety of vision correctionapplications, such as intraocular implants (IOLs), contact lenses, orspectacle (eyeglass) lenses.

BACKGROUND OF THE INVENTION

Multiorder diffractive (MOD) lenses are useful for bringing a pluralityof spectral components of different wavelengths to a common focus, andare described in U.S. Pat. No. 5,589,982, which is herein incorporatedby reference. The MOD lens has a structure of multiple annular zoneshaving step heights defining zone boundaries, which diffract light ofeach of the wavelengths in a different diffractive order to a commonfocus. Such a MOD lens has not been applied to bifocal optics for visioncorrection.

Conventional bifocal optics for spectacles are provided by lenses havinglower and upper regions of different refractive power for near anddistance (far) vision correction. For contact lenses and IOLs,multifocal refractive optics have been proposed with the anterior and/orposterior surfaces of a lens (or IOL optic) shaped to provide a centralzone, annular near zones, and annular distance zones of differentrefractive powers. Such bifocal refractive lenses do not utilizediffractive structures for near or distance vision correction. Examplesof multifocal refractive lenses for contacts and IOLs are shown in U.S.Pat. Nos. 6,231,603, 5,805,260, 5,798,817, 5,715,031, 5,682,223, andU.S. Publication No. U.S. 2003/0014107 A1. Other multifocal refractivelenses have other zones, such as pie, hyperbolic, or pin-wheel shapednear and distance zones, as shown in U.S. Pat. Nos. 5,512,220 and5,507,979, or spiral shaped zones, as shown in U.S. Pat. Nos. 5,517,260and 5,408,281. Moreover, refractive lenses are generally thicker thandiffractive lens for equivalent optical power, and thickness reductionis often desirable in ophthalmic applications, such as contact lensesand IOLs.

Non-MOD diffractive optics for multifocal ophthalmic applications existhaving a lens with a surface providing a diffractive structure ofconcentric zones of different step heights for near and far visioncorrection, such as described, for example, in U.S. Pat. No. 5,699,142.Another multifocal diffractive lens, described in U.S. Pat. No.5,748,282, has a similar diffractive structure with a region having areduced step height to reduce intensity of light from such region. Afurther multifocal diffractive lens is described in U.S. Pat. No.5,116,111 also has a similar non-MOD diffractive structure in which thebase power of lens may be provided by refraction of the lens. Thediffractive lenses of U.S. Pat. Nos. 5,699,142, 5,748,282, and 5,116,111lack the ability of the MOD lens to focus light of different wavelengthsto a common focus for either near or far vision correction by theirreliance on non-MOD structures. Other non-MOD optics may be segmented toprovide multiple regions, but are not multifocal. For example, U.S. Pat.No. 5,071,207 describes a non-MOD diffractive lens having pie-shapedsegments in which all the segments of the lens are limited to focusinglight to a common focus. Thus, prior approaches to multifocal or bifocaloptics have utilized refractive surfaces or non-MOD structures.

SUMMARY OF THE INVENTION

Accordingly, it is the principal object of the present invention toprovide bifocal diffractive lenses utilizing multiorder diffractive(MOD) structures to provide vision correction at near and far distances.

Another object of the present invention is to provide bifocal multiorderdiffractive lenses which may be adapted for use in a variety of visioncorrection applications, including contact lenses, intraocular implants(IOL), and spectacle lenses.

Still another object of the present invention is to provide bifocalmultiorder diffractive lenses using MOD structures which may haverefractive surfaces for additional power correction.

A further object of the present invention is to provide a bifocalmultiorder diffractive lens for correction of vision in which theperformance of the lens is tailored to the human perception of lightunder high (photopic) and low (scotopic) illumination.

Briefly described, the present invention embodies a lens body having oneor more first regions having a first multiorder diffractive structureproviding near vision correction, and one or more second regions havinga second multiorder diffractive structure providing distance visioncorrection, in which the lens defines an aperture divided between thefirst and second regions. Such one or more first regions may representone or more annular rings, or other portion of the lens, and the secondregion may occupy the portion of the lens aperture outside the firstregion, such as central region and one or more annular rings alternatingwith first region annular ring(s). The lens may be a single opticalelement having the first and second regions both located upon the samefront or back surface of the lens, or the first region located upon oneof the front or back surface and the second regions on the othersurface. The lens may also be provided by multiple optical elementsintegrated into the lens body having front and back surfaces and one ormore intermediate surfaces depending on the number of optical elements.The first and second regions are provided along the same or differentintermediate surfaces of the lens to divide the lens aperture. One orboth of the first and second multiorder diffractive structures may beoptionally optimized for performance for photopic and scotopic vision.

In other embodiments, a bifocal multiorder diffractive lens is providedby a single or multiple element lens body having a multiorderdiffractive structure for distance vision correction and one or morerefractive regions to add power for near vision correction, or a singleor multiple element lens body shaped for refractive power for distancevision correction and a multiorder diffractive structure to add powerfor near vision correction.

Each of the MOD structures of the lenses of the present inventiondirects different wavelengths of light to a single focus of an opticalpower for the desired vision correction. This MOD structure ischaracterized by multiple zones which define zone boundaries at whichlight incident on the diffractive structure experiences an optical phaseshift, and diffracts light of each of the wavelengths in a differentdiffractive order, m, such that m is greater than or equal to 1, to thesame focus. The zones may be radially spaced at r_(j) and said radii areobtained by solving the equation φ(r_(j))=2πp_(j) where φ(r_(j))represents the phase function for the wavefront emerging from thediffractive lens, and p represents the number of 2π phase jumps at thezone boundaries for one of the plurality of wavelengths where p is aninteger greater than 1. The MOD structure is described in more detail inthe above-incorporated U.S. Pat. No. 5,589,982.

The lenses of the present invention may be used in a variety ofophthalmic applications, such as a contact lens, a spectacle lens, orthe lens of an intraocular implant (IOL), or other optics useful forvision correction of the eye.

DETAILED DESCRIPTION OF THE DRAWINGS

The foregoing objects, features and advantages of the invention willbecome more apparent from a reading of the following description inconnection with the accompanying drawings, in which:

FIGS. 1A and 1B are plan diagrams of the two surfaces of a firstembodiment bifocal multiorder diffractive lens of the present inventionin which two different multiorder diffractive structures are provided onthe surface of FIG. 1B for near and distance vision correction, and nodiffractive structures are provide on the surface of FIG. 1A;

FIG. 1C is a sectional view of the lens of FIGS. 1A and 1B;

FIGS. 2A and 2B are plan diagrams of the two surfaces of a secondembodiment bifocal multiorder diffractive lens of the present inventionin which one multiorder diffractive structure is provided along anannular region on the surface of FIG. 2A for near vision correction, andsecond multiorder diffractive structure is provided on annular andcentral regions on the surface of FIG. 2B for distance visioncorrection;

FIGS. 3A and 3B are plan diagrams of the two surfaces of a thirdembodiment bifocal multiorder diffractive lens of the present inventionin which the surface of FIG. 3B has two multiorder diffractivestructures along two different regions providing distance and nearvision correction, respectively, and the surface of FIG. 3A has nodiffractive structures;

FIGS. 4A and 4B are plan diagrams of the two surfaces of a fourthembodiment bifocal multiorder diffractive lens of the present inventionin which each surface has a different diffractive multiorder structurealong a region dividing the aperture of the lens for near and distancevision correction;

FIG. 5 is a sectional view of a fifth embodiment bifocal multiorderdiffractive lens of the present invention having one surface with amultiorder diffractive structure for distance vision correction andrefractive curvature along the other surface of the lens for near visioncorrection;

FIGS. 6-8 are sectional views of other embodiments of bifocal multiorderdiffractive lenses having two optical elements integrated into a singlelens body;

FIGS. 9-14 are sectional views of further embodiments of bifocalmultiorder diffractive lenses having three optical elements integratedinto a single lens body in which the middle optical element may be air,liquid, or of a solid lens material;

FIG. 15 is a sectional view of an additional embodiment of a bifocalmultiorder diffractive lens having two optical elements integrated intoa lens body for use as a spectacle lens having a multiorder diffractivestructure for near vision correction, and refractive power of the lensbody for distance vision correction;

FIGS. 16 and 17 are a sectional views of a still further embodiment of abifocal multiorder diffractive lens having three optical elementsintegrated into a lens body for use as a spectacle lens having amultiorder diffractive structure between first and second elements inFIG. 16, and between the second and third elements in FIG. 17, andrefractive power of the lens body for distance vision correction; and

FIGS. 18, 19, and 20 are graphs of the efficiency versus wavelength forthree multiorder diffractive structures having different values of p, aninteger representing the maximum phase modulation as a multiple of 2π,where the peaks of the efficiency correspond with the peak of humanperception of light for photopic and scotopic vision.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the FIGS. 1A, 1B and 1C, a bifocal multiorder diffractive(MOD) lens 10 is shown having a lens body 11 with a first surface 12 anda second surface 13 in FIGS. 1A and 1B, respectively. Surfaces 12 and 13may represent the front and back surface of the lens, respectively.Surface 13 has a first annular region 14 with a MOD lens structureproviding a focal distance (or optical power) for near visioncorrection, and a second region 16 outside the first region 14 with aMOD lens structure having a focal distance (or optical power) for farvision correction. Region 16 represents a central portion 16 a and anannular portion 16 b. The MOD lens structures of regions 14 and 16 aresuch as described in the above incorporated U.S. Pat. No. 5,589,982,where the regions have zones with step heights providing the bifocalvision correction at powers in accordance with the eye of the lens userfor the desired focal distance. FIGS. 1A-1C represent one embodiment ofa bifocal MOD lens where the regions 14 and 16 are formed on the backsurface 13 of the lens to divide or split the aperture of lens 10, andthe front surface 12 has no diffractive power. The curvature of the lensbody 11 in FIG. 1C is for purposes of illustration, the lens body may beother shapes, such as a disk, depending on the particular ophthalmicapplication. Alternatively, the regions 14 and 16 may be provided on thefront surface 12 of the lens, and no power on the back surface 13. FIGS.2A and 2B represent the front and back surfaces of another embodiment oflens in accordance of the present invention. In this embodiment, bifocalMOD lens 10 has region 14 on the front surface 12 and region 16 on theback surface 13 of the lens to divide the aperture of the lens, ratherthan on the same surface, as in FIG. 1B. Alternatively, regions 14 and16 may be provided on back surface 13 and front surface 12,respectively, in FIGS. 2A and 2B. Further, although one annular region14 is shown, region 14 may have multiple annular regions, alternatingwith multiple annular portions of region 16.

FIGS. 3A and 3B show another embodiment of bifocal MOD lens 10 in whichregion 16 is formed along a crescent shaped portion substantiallyoccupying the upper part on the lens, and region 14 is formed on theremaining lower portion of the lens to divide the lens aperture.Similarly, regions 14 and 16 in FIGS. 3A and 3B may be on the samesurface 12 or 13, or may be split over surfaces 12 or 13 of the lens, asshown in FIGS. 4A and 4B. In FIGS. 3A, 3B, 4A and 4B, surfaces 12 and 13may represent the front and back surfaces of the lens, or vice versa.

FIG. 5 shows a further embodiment in a cross-sectional view of bifocallens 10 having along the entire surface 13 a MOD structure for distancevision correction, and a refractive curvature along annular region 17along surface 12 to add power for near vision correction without a MODstructure for near vision correction. Although a single annular region17 is shown, multiple annular regions may be provided along surface 12.Alternatively, the base power of the bifocal lens 10 may be provided byrefraction for distance vision correction, and the add power by the MODstructure on surface 13 for near vision correction

The lens 10 may be composed of transmissive material, such as typicallyused in the manufacture of contacts, optic portion of IOLs, orspectacles (e.g., plastic, silicone, glass, or polymers typically usedfor the particular contact, IOL, or spectacle application). Typicalprocesses providing diffractive optical surface, such as etching ormolding, may form the zones of the MOD structures of the lens. Forexample, single point diamond turning machinery from Precitech, Inc. ofKeene, N.H. may be used to provide MOD structures on one or moresurfaces of a lens. Although the lens 10 of FIGS. 1A, 1B, 1C, 2A, 2B,3A, 3B, 4A, 4B, and 5 may be used in a variety of ophthalmicapplications, they may be especially useful in the lens of an IOL byincorporation of haptic or support structures used with IOLs, as used inother typical IOL lenses, for example, see U.S. Pat. Nos. 6,406,494,6,176,878, 5,096,285, or U.S. patent application Publications Nos.2002/0120329 A1, 2002/0016630 A1, 2002/0193876 A1, 2003/0014107 A1, or2003/0018385 A1, or without typical haptic structures, as shown in U.S.Pat. No. 4,769,033. Also, regions 14 and 16 shown in the figures may beswitched on lenses 10, if desired, depending on the desired portions ofthe lens aperture divided between near and distance vision correction.FIGS. 1A-1D, 2A, 2B, 3A, 3B, 4A, and 4B show a single optical elementproviding the body of the lens. The lens 10 may also be provided usingmultiple optical elements integrated together to provide the body of thelens, as shown below.

Referring to FIGS. 6-8, embodiments of lens 10 are shown having twooptical elements 10 a and 10 b, in which a diffractive profile isprovided on an intermediate surface 18 representing the front surface 19a of optical element 10 b, or back surface 19 b of optical element 10 a,between front surface 20 and back surface 21 of the lens. The surfaces19 a and 19 b are shaped (i.e., one surface a diffractive profile andthe other surface the reverse diffractive profile) such that they matewith each other when optical elements are bonded (e.g. liquid adhesive),fused, or otherwise sealed together. Optical elements 10 a and 10 b aremade of different materials with different indices of refraction, suchthat light may properly be diffracted by the MOD structures of regions14 and 16. The advantage of providing the diffractive structures on anintermediate surface 18 of the lens is that the front and/or backsurface of the lens may be substantially smooth, and thus morecomfortable when such lens is used as a contact lens. FIG. 6 has adiffractive profile along surface 18 similar to FIG. 1B with a centralregion 16 and alternating annular regions 14 and 16 at increasingdiameters to the edge of lens 10, and the MOD structure of regions 14provide near vision correction and the MOD structure of regions 16provide distance vision correction. In the lens 10 of FIG. 6, refractivepower of the lens may be zero or minimal. FIG. 7 has annular refractiveregions 22 along surface 20 having curvature providing additional powerto the lens for near vision correction, and the entire surface 18 mayprovide a diffractive profile for distance vision correction without aMOD structure for near vision correction. In other words, in FIG. 7light passing through the refractive regions 22 provides power added tothe base power of the MOD structure on surface 18 to enable near visioncorrection. Although two refractive regions 22 are shown, one or morethan two annular regions 22 may be provided. FIG. 8 differs from FIG. 7in that the base power for distance vision correction is provided by therefractive curvature of the lens 10 body provided by optical elements 10a and 10 b, and along surface 18 are annular regions 14 with a MODstructure to add power for near vision correction without a MODstructure for distance correction.

Referring to FIGS. 9-14, embodiments of lens 10 are shown having threeoptical elements 10 c, 10 d, and 10 e in which a diffractive profile isprovided on an intermediate surface 24 between front surface 25 and backsurface 26 of the lens. Optical element 10 e represents a base, opticalelement 10 c represents a cover, which is bonded (such as by liquidadhesive), fused, or otherwise sealed to the base, and optical element10 d represents air, liquid, or solid lens material occupying theinterface between optical elements 10 e and 10 c. FIG. 9 shows theintermediate surface 24 on the back surface of optical element 10 chaving MOD structures of regions 14 and 16 segmenting the lens aperture,and is similar to FIG. 1B but with a central region 16 and alternatingannular regions 14 and 16 of increasing diameter to the edge of lens 10.Alternatively, intermediate surface 24 may represent the front surfaceof optical element 10 e facing optical element 10 d, as shown in FIG.10. Further, multiple intermediate surfaces 24 between adjacent elements10 c, 10 d, and 10 e may be provided and the central and annular regions16 provided on one of such intermediate surfaces, and annular regions 14on another of such intermediate surfaces to divide the aperture of thelens of FIG. 9 or 10. In the lens 10 of FIGS. 9 and 10 refractive powerof the lens may be zero or minimal, but additional refractive power fornear or distance vision may be added to the lens body. FIG. 11 shows alens having surface 24 on the back surface of optical element 10 c, andoptical elements 10 c and/or 10 e are shaped to provide refractivecurvatures providing a base power to the lens for distance visioncorrection. In FIG. 11, the diffractive profile of surface 24 hasannular regions 14 providing a MOD structure to add power for nearvision correction without a MOD structure for distance visioncorrection. FIG. 12 shows a lens 10 having surface 24 on the frontsurface of optical element 10 e, and having refractive curvatures oflens 10 of optical element 10 c and 10 e (and element 10 d if of a solidoptically transmissive material) to provide the base power for distancevision correction, and annular regions on surface 24 with a MODstructure for near vision correction. FIG. 13 shows a lens 10 withintermediate surface 24 on optical element 10 d and regions or rings 28upon the front surface of optical element 10 e with curvature addingrefractive power for near vision correction. FIG. 14 shows a lens 10having surface 24 on front of optical element 10 e and having regions orrings 29 upon the back surface of optical element 10 d with curvatureadding refractive power for near vision correction. In FIGS. 13 and 14,a MOD structure is provided on surface 24 for distance visionscorrection without a MOD structure for near vision correction.

In FIG. 9-14, when optical element 10 d is of a solid opticallytransmission material, rather than air or liquid, it has a shape havingreverse surface features to mate with diffractive profile of surface 24on either elements 10 c or 10 d, of if present, reverse surface featuresto mate with refractive features 28 or 29 along elements 10 e or 10 c,respectively. Further, when optical element 10 d is of a solid materialit may be bonded, fused, or otherwise sealed to optical elements 10 cand/or 10 e. Although lenses 10 of FIGS. 6-14 may be used in variousophthalmologic applications, they are especially useful for contactlenses.

Referring to FIG. 15, another embodiment of the bifocal multiorderdiffractive lens 10 is shown having two optical elements 10 f and 10 gintegrated into a single lens body for use as a spectacle lens and aregion 30 having a MOD structure for near vision correction, wherecurvatures along elements 10 f and 10 g provide refractive power fordistance vision correction. Region 30 is formed near the lower part ofthe lens 10 on either surface 31 a of optical element 10 f, or surface31 b of optical element 10 g. The optical element 10 f or 10 g nothaving such region 30 f is shaped having a reverse surface features fromregion 30 to mate with such region when optical elements 10 f and 10 gare joined together. Except for region 30, the back surface 31 a ofoptical element 10 f and front surface 31 b of optical element 10 g havethe same curvature such that they mate with each other when the opticalelements are bonded, fused, or otherwise sealed together.

Referring to FIGS. 16 and 17, embodiments of the bifocal multiorderdiffractive lens are shown having three optical elements 10 h, 10 i, and10 j integrated into a single lens body for use as a spectacle lens.Optical element 10 j represents a base, optical element 10 h representsa cover, which is bonded, fused, or otherwise sealed to the base, andoptical element 10 i represents air, liquid, or solid lens materialoccupying the interface between optical elements 10 h and 10 j. Region30 having MOD structure for near vision correction may be provided alongsurface 31 a of optical element 10 h or surface 31 b of optical element10 j, while curvature of optical elements 10 h and 10 j providerefractive power for distance vision correction. Optionally, adiffractive plate or member may provide region 30, which may be insertedin a space provided between optical elements 10 h or 10 j prior tojoining such elements, and bonded in such space by liquid adhesive orother joining means.

Lenses 10 of FIGS. 6-14 may be made of optically transmissive materials,such as plastic, silicone, glass, or polymer typically used to providelenses in ophthalmic applications. FIGS. 9, 11, and 13 show the coveroptical element 10 c as having edges short of the upper and lower edgesof the lens 10 for purposes of illustration, optical element 10 c, likein FIGS. 10 and 12, may extend to such upper and lower edges of thelens. When lens 10 of FIGS. 6-14 represents a contact lens, surfaces 21or 26 will contact and conform to the eye surface of the contact lenswearer, as typical of contact lens.

One advantage over bifocal refractive optics of comparable powers isthat the lens 10 having bifocal MOD structure is thinner, and morereadily foldable when part of the optic portion of an IOL duringimplantation.

The MOD structures in the embodiments of lens 10 shown in the abovedescribed figures may be designed for manufacture in accordance with theequations shown in the above-incorporated U.S. Patent. In suchequations, n represents the index of refraction between the material(within which the phase profile of the MOD structure is made) and air.However, in the present application, MOD structures may interface withmaterials other than air, such as liquid (e.g., in the lens, or withinwhich the lens may be immersed as may be the case of an IOL in the eyefor the lens having MOD structure on an outer lens surface), or materialof adjacent lens elements. Thus, the same equations may be used with“n−1” representing the difference in the index of refraction between thematerial that the MOD structure will be made and such other material inthe particular optical design of lens 10.

The MOD structures in the embodiments of lens 10 shown in the abovedescribed figures may be fashioned such that the efficiency of thestructure is optimized for human eyes perception of light wavelengthsunder high illumination, referred to as photopic vision, or lowerillumination, referred to as scotopic vision, as generally occurs duringday and night natural illumination, respectively. This is achieved byselecting the MOD number p of the MOD lens structure. The optical designof the MOD structure and the variable p is discussed in theabove-incorporated U.S. Patent. Photopic efficiency describes thespectral response under bright light conditions. The peak photopicefficiency is at λ=555 nm. Scotopic efficiency describes the spectralresponse under low light conditions. The peak scotopic efficiency is atλ=507 nm.

The MOD structures of the lens 10 are designed such that the wavelengthsbrought to a common focus with high efficiency correspond to thesewavelengths. Start by choosing the design wavelength λ₀ to be one(either photopic or scotopic) of these peaks, for example, λ₀=555 nm forphotopic. The other wavelengths with the same focal length are given by$\lambda_{peak} = \frac{p\quad\lambda_{0}}{m}$(See Eq. (8) in the above incorporated U.S. Patent.) So to bring awavelength λ_(peak) to the same focus as wavelength λ₀, p and m arefound such that $\frac{\lambda_{peak}}{\lambda_{0}} = \frac{p}{m}$where m is the order number, and p is an integer representing themaximum phase modulation as a multiple of 2π.

For photopic and scotopic peaks, p/m is needed to be 507/555 or 0.914.Since p and m are integers, this equation may not be satisfied exactlyfor small values of p and m, but approximate solutions for these valuesmay be found. For example, these values may be

-   -   p=11, m=12;p/m=0.917    -   p=21, m=23;p/m=0.913    -   p=32, m=35; p/m=0.914

The efficiency curves for these three cases are graphed in FIGS. 18, 19,and 20, respectively, along with the efficiency curves of the human'seye perception of wavelength in bright light, the photopic response, anddim light, the scotopic response. For each MOD structure, a peak alignswith peak scotopic efficiency and another peak aligns with photopicefficiency, as indicated by numerals 32 and 33, respectively. Thus, theamount of light diffracted is maximized at such wavelength for low andhigh illumination. In the absence of such optimization of the MODstructures on lens 10, the user of the lens may not view lightcorresponding to the peak scotopic and photopic efficiency of the eye,and thus the perceived intensity of the light from such a lens wouldappear less to the user than if the MOD structures were so optimized.Although such optimization for photopic and scotopic vision aredescribed for MOD structures in the above bifocal lens 10, theoptimization may be provided in a lens having a single MOD structure orany number of MOD structures.

In the MOD structures described for embodiments of lens 10 in the abovedescribed figures, astigmatism may also be corrected by use ofnon-circular zones (hyperbolic or elliptical) in a MOD structuredescribed in the incorporated U.S. Patent, such as described in U.S.Pat. No. 5,016,977 in non-MOD diffractive structures.

EXAMPLE 1

Consider an ophthalmic lens prescription requiring a correction of −7diopters for distance vision, with a +2 diopter add power for nearvision. Thus, the two powers (denoted by φ) of the lens areφ_(distance)=−7Dφ_(near)=−5D (=−7+2)The radial locations (r_(j)) of the diffractive zones from the center ofthe lens are given by$r_{j} = \sqrt{\frac{2j\quad p\quad\lambda_{0}}{\phi_{0}}}$where j is the zone number, p is the MOD number, λ₀ is the designwavelength, and φ₀ is the desired optical power of the lens. [See Eq.(1) of the above-incorporated U.S. Patent, with φ₀=1/F₀.]

In this example, λ₀=555 nm (peak of photopic response). If p=11, thezone radii within a clear aperture diameter of 12 mm for the distancepower are Distance power (−7 D) ZONE NUMBER (j) ZONE RADIUS (r_(j)) 11.320714 2 1.867772 3 2.287544 4 2.641428 5 2.953206 6 3.235076 73.494281 8 3.735544 9 3.962142 10 4.176465 11 4.380313 12 4.575088 134.761902 14 4.941660 15 5.115104 16 5.282856 17 5.445444 18 5.603315 195.756859 20 5.906413

Similarly, for the near power, the zone radii are Near power (−5 D) ZONENUMBER (j) ZONE RADIUS (r_(j)) 1 1.562690 2 2.209977 3 2.706658 43.125380 5 3.494281 6 3.827793 7 4.134489 8 4.419955 9 4.688070 104.941660 11 5.182856 12 5.413317 13 5.634359 14 5.847051In this example, two different MOD structures are shown for twodifferent prescriptions to correct distance and near vision. The belowexample shows that such prescriptions may be combined in a lens toprovide a multiorder diffractive bifocal lens.

EXAMPLE 2

To construct the bifocal MOD lens along the same surface, as shown inFIGS. 1A-1C, all the diffractive power is contained in circular/annularregions of one surface of the lens. The distance power is contained inregions 16 a and 16 b of FIG. 1B, while the near power is contained inregion 14. We choose the radius of region 16 a to be 2 mm, the outerradius of region 14 to be 4 mm and the outer radius of region 16 b to be6 mm. Then, the zone locations for the bifocal lens are the radii of theindividual power components that lie within these region boundaries.There are no diffractive zones on the other side of the lens. Zonelocations for bifocal MOD lens ZONE NUMBER (j) ZONE RADIUS (r_(j)) 11.320714 distance 2 1.867772 distance 3 2.209977 near 4 2.706658 near 53.125380 near 6 3.494281 near 7 3.827793 near 8 4.176465 distance 94.380313 distance 10 4.575088 distance 11 4.761902 distance 12 4.941660distance 13 5.115104 distance 14 5.282856 distance 15 5.445444 distance16 5.603315 distance 17 5.756859 distance 18 5.906413 distanceNote that this is one way to combine the zones from the two individualpower; other combinations are possible.

EXAMPLE 3

Another option is to place the near power on one surface of the lens andthe distance power on the other surface, as in the lens of FIGS. 2A and2B. In this embodiment, the zone locations are First Surface ZONE NUMBER(j) ZONE RADIUS (r_(j)) 1 2.209977 near 2 2.706658 near 3 3.125380 near4 3.494281 near 5 3.827793 near

No diffractive zones for radius less than 2.0 mm or radius greater than4.0 mm. Second Surface ZONE NUMBER (j) ZONE RADIUS (r_(j)) 1 1.320714distance 2 1.867772 distance 3 4.176465 distance 4 4.380313 distance 54.575088 distance 6 4.761902 distance 7 4.941660 distance 8 5.115104distance 9 5.282856 distance 10 5.445444 distance 11 5.603315 distance12 5.756859 distance 13 5.906413 distance

No diffractive zones for radius greater than 2.0 mm and less than 4.0mm.

For all of the above examples, the height of the zones is given by$h = \frac{p\quad\lambda_{0}}{{n_{lens}\left( \lambda_{0} \right)} - {n_{medium}\left( \lambda_{0} \right)}}$[See Eq. (4) of above-incorporated U.S. Patent.]

If the lens is in air, then n_(medium)(λ₀)=1.0. Also, if the lens isconstructed of a material with a refractive index of n_(lens)(λ₀)=1.5,this results in a height of h=12.21 μm, since in these examples p=11 andλ₀=555 nm. As these examples show, different MOD structures may beproduced for lens 10 having the particular desired optical power thatmay lie on the same or different lens surfaces of the front or backsurface of the lens, or on an interior surface in the case of amulti-element lens. Although in Examples 2 and 3 a single annular regionprovides near vision correction, multiple annular regions for nearvision correction may also be provided, which in the case of Example 2divide the lens aperture with annular regions of the MOD structure fordistance vision correction.

In summary, lens 10 may have a segmented aperture providing the bifocalvision correction. Each point in the aperture of the lens only producesa single lens power. The bifocal behavior is provided by havingdifferent areas of the lens aperture of different optical powers. Thissegmentation may be done on one side or on two sides of the lenssubstrate, as described earlier. When segmentation is done on two sides,the corresponding area on the non-diffractive side has no diffractivepower (FIGS. 2A, 2B, 4A, 4B). The power split (i.e., the fraction of theaperture providing distance vision correction and the fraction providingnear vision correction) is determined by the fraction of the aperturethat is covered by each diffractive lens. Although this ratio will befixed at manufacture, in use it will be affected by the size of the eyepupil. The aperture may be divided by concentric annular zones, or otherdivisions of the aperture may be provided, such as shown in FIGS. 3A,3B, 4A, and 4B. Also, even in a bifocal with only two distinct powers,each power may be provided in more than one optical zone of the lens, inorder to maintain the desired power balance over a range of pupil sizes.

In other bifocal lenses described above, a base power may be providedover the entire lens by either refractive (non-diffractive) optionalstructures, or MOD structures, and add power in a segmented lens portionof a refractive or MOD structure, as in FIGS. 5, 7, 8, and 11-14. Thelens 10 having such a hybrid refractive and MOD structures are oftenuseful for bifocal prescriptions where only a relatively small amount ofadd power (˜1 to 2.5 diopters) is required for near vision correction.This additional power can be provided by a weak lens, i.e., a surfacewith a large radius of curvature or, equivalently, small curvature,while distance vision correction is provided by a MOD structure of theappropriate power. A portion of the lens aperture has a weak refractivesurface that provides the add power. The refractive zone (or zones) islocated on the opposite side of the lens from the diffractive surface.As a result of the small curvature, the effect on the thickness would berelatively small. An example cross-section of the lens utilizing anannular refractive zone is shown in FIG. 5. As also described above, ahybrid refractive and MOD diffraction lens may have the add powerprovided by a diffractive component added to a base refractive lens.However, this may increase the thickness of the lens.

Although the lenses described herein are for bifocal lenses to providetwo optical powers, it may be extended to trifocal or further number ofoptical powers by providing additional alternating annular regions withsuch powers, or refractive regions of different add powers to adiffractive MOD structure base power. Further, each MOD structure isdesigned for a particular optical power at a design wavelength, invision applications involving illumination of multiple wavelengths, thepower represents a nominal optical power over the range of differentwavelengths diffracted by the MOD structure to a common focus, thus atdifferent wavelengths the optical power lies within a range near theoptical power at the design wavelength.

From the foregoing description, it will be apparent that there has beenprovided a bifocal multiorder diffractive lenses for vision correctionusing MOD structures. Variations and modifications in the hereindescribed device in accordance with the invention will undoubtedlysuggest themselves to those skilled in the art. Accordingly, theforegoing description should be taken as illustrative and not in alimiting sense.

1-23. (canceled)
 24. A bifocal multiorder diffractive lens comprising: alens body shaped to refract light to provide distance vision correction,and at least one multiorder diffractive structure for adding power tosaid lens for near vision correction.
 25. The lens according to claim 24wherein said lens body has a front and back surface and said lens bodyis provided by two or more optical elements, and has a surface of one ofsaid optical elements, between said front and back surfaces, providingsaid multiorder diffractive structure.
 26. The lens according to claim24 wherein said lens body is provided by multiple optical elementssuccessively adjacent to each other, and two of said adjacent opticalelements each have a surface facing each other, and said multiorderdiffractive structure is provided along a region upon the surface of oneof said two adjacent optical elements.
 27. The lens according to claim24 wherein said lens body is provided by multiple optical elementssuccessively adjacent to each other, and said multiorder diffractivestructure is provided upon a member positioned between two of saidadjacent optical elements.
 28. The lens according to claim 24 whereinsaid lens body is provided by a single optical element.
 29. Themultiorder diffractive lens according to claim 24 wherein one or moresaid diffractive structures is in accordance with wavelengths for bothphotopic and scotopic vision.
 30. The multiorder diffractive lensaccording to claim 29 wherein said photopic and scotopic vision eachhave a wavelength of peak efficiency, and the wavelength of peakefficiency for both photopic and scotopic vision aligns with awavelength of peak efficiency for each of said diffractive structures.31. The multiorder diffractive lens according to claim 24 wherein one ormore of said diffractive structures corrects for astigmatism.
 32. Abifocal multiorder diffractive lens comprising: a lens body having amultifocal diffractive structure for distance vision correction, and oneor more refractive regions for adding power to said lens for near visioncorrection.
 33. The multiorder diffractive lens according to claim 32wherein said lens body is provided by a single optical element, and saidlens body has a first surface having said diffractive structure and asecond surface having said one or more refractive regions.
 34. Themultiorder diffractive lens according to claim 32 wherein said lens bodyis provided by multiple optical elements.
 35. The multiorder diffractivelens according to claim 34 wherein said diffractive structure isprovided on an internal surface of said lens along one of said multipleoptical elements.
 36. The multiorder diffractive lens according to claim32 wherein said diffractive structure is in accordance with wavelengthsfor both photopic and scotopic vision.
 37. The multiorder diffractivelens according to claim 36 wherein said photopic and scotopic visioneach have a wavelength of peak efficiency, and the wavelength of peakefficiency for both photopic and scotopic vision aligns with awavelength of peak efficiency for said diffractive structure.
 38. Themultiorder diffractive lens according to claim 32 wherein saiddiffractive structure corrects for astigmatism. 39-49. (canceled) 50.The multiorder diffractive lens according to claim 24 further comprisingone or more regions along said lens body each having said multiorderdiffractive structure.
 51. The multiorder diffractive lens according toclaim 34 wherein said refractive regions are provided on an internalsurface of said lens along one of said multiple optical elements. 52.The multiorder diffractive lens according to claim 32 wherein saidrefractive regions are provided on an outer surface of said lens alongone of said multiple optical elements.
 53. The multiorder diffractivelens according to claim 34 wherein said refractive regions anddiffractive structure are each provided on a different internal surfaceof said lens along different ones of said multiple optical elements. 54.The multiorder diffractive lens according to claim 24 wherein saidmultiorder diffractive structure directs light in a plurality ofdifferent wavelengths in different diffractive orders to a single focusin accordance with said add power.
 55. The multiorder diffractive lensaccording to claim 54 wherein said multiorder diffractive structure ischaracterized by a plurality of zones which define zone boundaries atwhich light incident on the diffractive structure experiences an opticalphase shift, and which diffract light of each of said wavelengths in adifferent diffractive order, m, such that m≧1, to the focus for thediffractive structure.
 56. The multiorder diffractive lens according toclaim 24 wherein said lens element is part of one of an intraocularimplant, contact lens, or spectacle lens.
 57. The multiorder diffractivelens according to claim 24 wherein said diffractive structure has peakefficiencies at wavelengths corresponding to selected wavelengths ofpeak operation efficiencies.
 58. The multiorder diffractive lensaccording to claim 57 wherein said selected wavelengths of peakoperation efficiencies are two in number and are associated withphotopic and scotopic vision, respectively.
 59. The multiorderdiffractive lens according to claim 32 wherein said multiorderdiffractive structure directs light in a plurality of differentwavelengths in different diffractive orders to a single focus inaccordance with said distance vision correction.
 60. The multiorderdiffractive lens according to claim 59 wherein said multiorderdiffractive structure is characterized by a plurality of zones whichdefine zone boundaries at which light incident on the diffractivestructure experiences an optical phase shift, and which diffract lightof each of said wavelengths in a different diffractive order, m, suchthat m≧1, to the focus for the diffractive structure.
 61. The multiorderdiffractive lens according to claim 32 wherein said lens element is partof one of an intraocular implant, contact lens, or spectacle lens. 62.The multiorder diffractive lens according to claim 32 wherein saiddiffractive structures has peak efficiencies at wavelengthscorresponding to selected wavelengths of peak operation efficiencies.63. The multiorder diffractive lens according to claim 62 wherein saidselected wavelengths of peak operation efficiencies are two in numberand are associated with photopic and scotopic vision, respectively. 64.An optical element comprising: a lens body; at least one multiorderdiffractive structure for directing light in a plurality of differentwavelengths in different diffractive orders to a common focus inaccordance with a first optical power; and said lens body having arefractive body or at least one refractive region providing a secondoptical power, in which optical element is multifocal is accordance withsaid first and second optics powers.
 65. The optical element accordingto claim 64 wherein said second optical power provides distance visioncorrection, and said first optical power provides near visioncorrection.
 66. The optical element according to claim 65 furthercomprising one or more regions along said lens body each having saidmultiorder diffractive structure.
 67. The optical element according toclaim 64 wherein said first optical power provides for distance visioncorrection, and said second power provides adds power to said firstoptical power for near vision correction.
 68. The optical elementaccording to claim 64 wherein one of said refractive body or saidmultifocal diffractive structure corrects for astigmatism.
 69. Theoptical element according to claim 64 wherein said diffractivestructures has peak efficiencies at wavelengths corresponding toselected wavelengths of peak operation efficiencies.
 70. The opticalelement according to claim 64 where in said lens body is provided by asingle or multiple optical elements.